Numerous types of nonwoven disposable absorbent articles are commercially available, and are manufactured for use in the absorption and containment of bodily waste such as urine and feces. Typical of such articles are disposable diapers for infants, and undergarments for incontinent adults. In the construction of such disposable articles, an inner leg gather or cuff is employed to prevent leakage of the bodily waste from around the user's legs. During use, this cuff or flap is held in place with one or more elastic bands surrounding the leg. These elastic bands are typically held in place and attached to the disposable article by a hot melt adhesive.
While a wide range of hot melt adhesive compositions are known and used in the construction of disposable articles, it is also well known that a hot melt adhesive used for bonding in a particular use or application may be completely unsuitable for other uses or applications. Thus, various hot melt adhesive compositions are used in the construction of disposable articles. For example, it is well known that polyolefin based hot melt adhesives are suitable for the construction of diapers, particularly in the bonding of polyethylene films, or the like, to tissue or nonwoven substrates in the production of such articles. However, it is also known that polyolefin based hot melt adhesives are not suitable for bonding of the elastic bands in the diapers because creep resistance is insufficient for such an application. For this reason, hot melt adhesives based on styrene such as styrene-isoprene-styrene (SIS) block copolymers or styrene-butadiene-styrene (SBS) block copolymers are used. These block copolymer adhesives, however, also possess shortcomings such as viscosity instability which manifests itself at elevated temperature.
Another shortcoming is that these block copolymers lose most of their bond strength upon exposure to mineral oil or other oil based ointments. Mineral oil and other oil based ointments are often used on infants to treat skin rashes, and thus prior hot melt adhesive compositions, upon exposure thereto, experience adhesive bond failure. As a result, the elastic leg bands may actually let loose from the diaper resulting in complete failure and break down of the inner leg cuff. Therefore, an adhesive that is capable of withstanding exposure to mineral oil or other oil based ointments while still providing sufficient bond strength for elastic band attachment in the inner leg cuff would be highly desirable.
Manufacturers of nonwoven disposable articles, such as diapers, would also prefer using only a single hot melt adhesive in the manufacture of such articles. Clearly, the use of two or more hot melt adhesives on the same article poses some problems such as different handling procedures, clean up procedures, etc. which the manufacturer would prefer to avoid. Therefore, a single adhesive that is capable of performing bonding functions in both construction applications as well as elastic attachment applications in nonwoven disposable articles would be highly desirable.